Summary

Frost risk is limiting the adoption of pulse crops in some regions of South Australia. New agronomic approaches that provide protection to crops or avoid frost during critical reproductive stages could increase the adoption of pulse crops in frost prone environments. The project demonstrated that frost damage could be mitigated with mixed cropping in some years for high value pulse crops, with the level of pod protection dependent on canopy architecture. Sowing later mitigated pod damage in chickpea in 2023 but did not impact grain yield.

Background

Frost is a major abiotic stress in cropping systems in southern Australia and limits the diversity of pulse crops adopted in high frost risk environments. This project investigated new techniques – mixed cropping and time of sowing – to mitigate frost in SA cropping systems. The aim was to help growers better understand mixed cropping systems and using strategies like mixed cropping and delayed sowing to increase productivity and reduce input costs while improving soil health.

Research Aims

The core objective of the project was to develop and extend agronomic strategies for frost management in pulses to increase overall productivity, reduce seasonal risk factors and support the incorporation of a range of break crop options into farming systems.

In The Field

Field trials were conducted at Farrell Flat in 2021 to 2023 investigating two or three species intercropping. Two species mixed crop treatments included lentil with either barley, faba bean, canola or canola (canola removed with hedge trimmer just below lentil canopy height prior to canola flowering to reduce late season crop competition). Three way species mixes were lentil with faba bean plus barley or lentil with faba bean plus canola. Mixed treatments were compared to single crops of lentil, barley, canola and faba bean. Biomass cuts and frost damage assessments were undertaken.

Time of sowing (TOS) trials were also conducted at Farrell Flat in 2022 and 2023 with six chickpea varieties and three bean varieties sown in mid-June (TOS1) or late July (TOS2). Biomass and grain yield were recorded.

Results

In the mixed cropping trials in 2021, there was good biomass production in all crops due to a favourable season. Two consecutive frost events were recorded during lentil podding that caused visible pod damage.

Higher biomass was linked with higher levels of frost protection. The lentil + faba bean + canola and lentil + faba bean treatments showed the lowest levels of pod damage – five times less than monoculture lentil. The lentil + faba bean mix reduced damage from a frost during podding from 31 per cent to 4 per cent. However, pod damage was higher in the lentil + canola and lentil + barley treatments than monoculture lentil.

In 2023, faba bean establishment was poor which was reflected in low biomass levels. A single frost event during lentil podding caused visible pod damage. A higher level of pod damage was recorded in both the lentil + faba bean + canola and the lentil + faba bean treatments compared to 2021. This was most likely due to the poor faba bean canopy, but pod damage was still lower than monoculture lentil. Again, the lentil + barley treatment had higher pod damage than monoculture lentil.

No frost events resulted in visible pod damage in 2022.

In 2022 TOS trials, TOS1 generated higher biomass than TOS2 in all faba bean varieties and PBA Royal chickpea. Similarly, TOS1 recorded higher grain yield than TOS2 in all faba bean varieties except Narbon, whereas chickpea, except PBA Royal, recorded similar or higher grain yield at TOS2.

In 2023 TOS trials, TOS1 favoured higher biomass in most varieties except PBA Striker and PBA Royal. Only faba beans recorded an increase in grain yield at TOS1 compared to TOS2 due to the tighter finish and lack of soil moisture late in the 2023 season. Visual differences in chickpea grain quality were observed, with varieties sown at TOS2 having less frost damage than those sown at TOS1.